1. Field of the Invention
The present invention relates to an apparatus for use in manufacturing of chip type electrical parts, and particularly to a breaking apparatus for dividing into bar-shaped boards a ceramic board having break grooves.
2. Description of the Related Art
As shown in FIGS. 8 and 9, in a breaking apparatus 100 for dividing a ceramic board 200 into bar-shaped boards 210, right and left feeding belts 110 are disposed in parallel to each other, and a press belt 120 is overlaid on each of the feeding belts 110 from the upper side. A ceramic board 200 having break grooves 201 formed therein is fed by both the belts 110 and 120 while sandwiched between both the belts 110 and 120. A break pulley 300 is pressed against the lower surfaces of each of the feeding belts 110 to bend the belts 110 and 120.
The ceramic board 200 is divided into many bar-shaped boards 210 along the break grooves 201 by the belts 110, 120 which are bent by the break pulleys 300. Further, the back surface of each feeding belt 110 is provided with a rack-shaped tooth row 130 having many teeth 140 arranged at fixed intervals so that the press face of the break pulley 300 does not slip along the back surface of the feeding belt 110, thereby preventing the ceramic board 200 during feeding from being slipped and positionally arranged in an offset manner. Further, a pinion-shaped gear tooth row 310 comprising many gear teeth 320 is projected on the outer periphery of the break pulley 300 so that the gear teeth 320 are engaged with the gear teeth of the feeding belts 110.
The tooth row 130 of the feeding belt 110 comprises thick projecting portions 141 which are formed as the teeth 140 and are stiff, and recess portions 142 which are formed between the respective teeth 140 and are flexible. When the feeding belts 110 are bent along the peripheral surface of the break pulley 300, the curvature of the feeding belts 110 is smaller at the projecting portions 141 thereof and larger at the recess portions 142 thereof.
Accordingly, when the ceramic board 200 sandwiched between each feeding belt 110 and each press belt 120 just passes over the bent portions of the feeding belts 110 in the dividing process of the ceramic board 200, if the breaking groove 201 is located at the recess portion 142, the ceramic board 200 is readily divided because the curvature is large. However, if the breaking groove 201 is located at the projecting portion 141, the ceramic board 200 is not accurately divided into the bar-shaped board 210 or cracks occur in the divided face because the curvature is small.
Accordingly, the break grooves 201 of the ceramic board 200 are desired to be located at the recess portions 142 having the larger curvature at all times.
However, the break grooves 201 of the ceramic board 200 are not necessarily located at the recess portions 142 having the larger curvature at all times during feeding, and it is randomly determined whether any breaking groove 201 is located at the projecting portion 141 having the small curvature or at the recess portion 142 having the large curvature.
Particularly, since the gear teeth 320, in the respective gear teeth rows 310 which are provided on the right and left break pulleys 300, are arranged so as to be positionally coincident with each other, the probability that any break groove 201 is located at the portion of the tooth 140 in each tooth row 130, that is, at the projecting portion 141 having the small curvature is approximately equal to 1/2, and thus the division efficiency is lowered.
In order to prevent the foregoing trouble, the press force of the press belts 120 may be enhanced. However, if the press force is enhanced, some cracking occurs in the travel direction (feeding direction) of the ceramic board 200, resulting in defective articles. Further, if the press force of the press belts 120 are enhanced, the press force is also transmitted and the feeding belts 110 and severely wears the teeth 140 in the teeth rows 130 provided on the feeding belts 110 and the gear teeth 320 in the gear teeth rows 310 provided on the break pulleys 300, and although various countermeasures have been taken, such severe wearing cannot be sufficiently prevented.